The invention relates to subsea wells and in particular to a wellhead system whereby for a slight initial expense, accessory modules may be used to turn an exploratory well into a production well.
When it is known in subsea drilling that a well will successfully and economically produce oil, substantial investment is made in the guide base used during the drilling. This investment is directed to strengthening the guide base and locating various components so that the well may be produced by remotely attached equipment.
The large majority of subsea wells, however, are exploratory either as a wildcat or for the purpose of defining the area of an oil field. These exploratory wells use a standard permanent guide base with no provisions for attachments. Should one wish to produce oil from the conventional exploratory well, there are several alternatives at specific geographical locations. A spool piece may be attached to the wellhead and the conductor run up to the surface where a fixed platform carries a surface tree, with production being similar to a land based well. In other locations it is possible to send divers to the seabed so that the various alignment structures may be clamped to the guide base and erected at that location. The use of the spool piece is not acceptable at all locations, and the use of divers is not only very expensive and dangerous but impractical at substantial depth.